We Finally Understand How Anakin Skywalker Was Able To Build C-3PO
The original "Star Wars" film, now subtitled "A New Hope," wasn't always movie four in a nine movie trilogy. In fact, in the days leading up to the release of "A New Hope," franchise creator George Lucas was so unsure about whether or not "Star Wars" would succeed that he wrote a (thankfully) unproduced sequel, titled "Splinter of the Mind's Eye," explicitly intended to be filmed on a low budget, so that the series could continue even in spite of what he expected might be a low box office return.
Only after "Star Wars" was a certified hit could George Lucas move forward with his plans for a multi-film franchise. That said, even then, certain story oddities persisted, inserted without necessarily much thought as to their broader canonical implications. In "The Empire Strikes Back," for example, Luke (Mark Hamill) and Leia (Carrie Fisher) kiss, which doesn't seem weird at the time — but then, "Return of the Jedi" reveals that they're siblings, which was, unsurprisingly, unplanned at the time of the conception of their "Empire Strikes Back" romance.
Another minor plot point that still stands out today, due to its broader canonical impact, is the fact that a young Anakin Skywalker (Jake Lloyd) single-handedly built C3-PO (voiced by Anthony Daniels).
In "The Phantom Menace," by which point Anakin has nearly completed C-3PO, Anakin is nine years-old. Now, 22 years after the release of "The Phantom Menace," a new canonical "Star Wars" work has finally shed some light on how a child might have constructed such a complex protocol droid from scratch.
Being good at machines is now an official force power
The Force ability with which Anakin was likely able to so adeptly work with machines despite his young age was revealed in children's book "The High Republic: Race to Crashpoint Tower," which is part of a larger, ongoing series of "High Republic" books.
According to an article about the book on Screen Rant, "Race to Crashpoint Tower" introduces a character named Ram Jomaran. He's a Padawan, or Jedi-in-training, meaning that his force abilities are not yet well-developed, similar to Anakin upon his introduction in "The Phantom Menace." Nevertheless, the book explains that Ram can connect on a deep level to technology thanks to the nature of his particular connection to the Force.
Those overtly concerned with "Star Wars" canon, then, can assume that Anakin possesses that same affinity. Building C-3PO is far from Anakin's sole connection to technology — he also builds a pod racer that he pilots in "The Phantom Menace," gains a robotic arm in "Attack of the Clones," and, of course, becomes a cyborg upon his transformation into Darth Vader. While some of these instances are of Anakin becoming part-technology himself rather than building anything, a deeper Force connection to all things mechanical still makes perfect sense, given his immense power as Darth Vader, requiring the manipulation of an entire robotic suit of armor.
Now, as for why Darth Vader seemingly doesn't recognize his very own droid when he reencounters him in the original trilogy? That's a mystery for another day.